The present invention relates to a device for mounting thin cylindrical objects, which after having been mounted are adapted to be used for any kind of rotary working operation.
The invention can be used in several different fields, but for the sake of simplicity the invention will be described with the mounting of rotary screen for rotary screens printing operations.
Rotary screens conventionally used in rotary screen printing operations comprise a thin cylinder of nickel or any other suitable metal which is prepared by electro-plating and if necessary etching. The cylinder carries the design for the image to be printed in the form of a screen having various size holes. The cylinder thus provided has a thickness of about a millimeter and it may often have a length of more than 2 meters. Due to the relative thinness of the material and the length in comparison to its diameter, it has to be stretched or tensioned relatively strongly in the axial direction in order that the cylinder will not collapse during the printing operation or yield at the central parts thereof whereby printing is not possible. For this purpose, the cylinder or the rotary screen is provided with mounting ends at the opposite ends thereof, and the axial stretching is provided by an axial movement of the said mounting ends.
For technical reasons during printing operations, the rotary screen must have a completely smooth outer surface without any projecting parts, and the mounting of the rotary screen on the mounting ends should be accomplished in a manner such that the screen is retained by internal rather than external mounting means.
A known method of mounting a rotary screen on mounting ends or means comprises providing the mounting ends with a cylindrical rim of substantially the same thickness as the rotary screen and having the same outer circumference as the inner circumference of the rotary screen. The rotary screen is mounted over the rims of the mounting ends and secured by suitable means such as any suitable glue. If desired, a thin strip of tape may be applied round the outer joint between the screen and the rim of the mounting ends. The rotary screen so mounted is then installed and secured in the printing machine and a relatively strong tensioning or stretching is applied in the axial direction so that the rotary screen is kept stretched in its cylindrical form, whereby printing may be conducted.
The said known method gives good results, but the method has some disadvantages. The disadvantages are particularly related to the fact that the rotary screen has to be saved after the printing operation in order to be used again for printing operations. This avoids the expensive and time consuming operation of providing and mounting of one or more new rotary screens for each print pattern. The glued connection between the mounting ends and the rotary screen must be very strong in order to make possible the strong stretching between the mounting ends without pulling the glued joints apart. Since the glued mounting ends cannot be released from the rotary screen after the printing, the storing of the rotary screens requires large storage room. Furthermore, for each rotary screen, two mounting ends are required.
It has therefore been a disideratum of the industry for a method of releasably mounting rotary screens on mounting ends, whereby the necessary storage space for the rotary screens could be reduced and at the same time the method would provide the reusing of the mounting ends for other rotary screens.
An essential problem in the attempts of eliminating the disadvantages in the said known method is that the mounting ends ought to be as light in weight as possible since there is otherwise a risk that the rotary screen would collapse or at worst be broken when the rotary screen mounted on the mounting ends is lifted for installation in the printing machine. The thin rotary screen cylinder is very easily damaged and the lifting thereof is only practical at the mounting ends. Every tendency for increase of weight of the mounting ends therefore increases the risk of breaking the rotary screen when lifting the screen together with its mounting ends.